Quality
Sometime is very hard to explain is it product printed well.
How we see color is different topic but usualy we have several cases.
WYSYWIG
Wysywig or what you see is what you get is big myth in computer era.
Customer work on files and look on his monitor. Customer expect that what he see on his monitor printer must reproduce and if it's not it's printer fault.
There is several reason why you can't achieve same color reproduction on printing press as you see on your monitor. Mainly there is mistakes which fall in different categories.
Device fault
Cheap low quality monitor
Impromer monitor setup
Uncalibrated monitor
Software fault
Improper color setup in desktop application
Invalid or legacy ICC profile selection.
Wrong softproof setup
Customer did not use softproof
Approvment of digital data in Email program
Usage of Acrobat Reader insted of Acrobat Pro